Iron is one of the most common elements on earth. Nearly every construction of man contains at least a little iron. It is also one of the oldest metals and was first fashioned into useful and ornamental objects at least 3,500 years ago.Earth's most important iron ore deposits are found in sedimentary rocks. They formed from chemical reactions that combined iron and oxygen in marine and fresh waters. The two most important minerals in these deposits are iron oxides: hematite (Fe2O3) and magnetite(Fe3O4). These iron ores have been mined to produce almost every iron and steel object that we use today - from paper clips to automobiles to the steel beams in skyscrapers. Nearly all of Earth's major iron ore deposits are in rocks that formed over 1.8 billion years ago. At that time Earth's oceans contained abundant dissolved iron and almost no dissolved oxygen. The iron ore deposits began forming when the first organisms capable of photosynthesis began releasing oxygen into the waters. This oxygen immediately combined with the abundant dissolved iron to produce hematite or magnetite. These minerals deposited on the sea floor in great abundance, forming what are now known as the "banded iron formations." The rocks are "banded" because the iron minerals deposited in alternating bands with silica and sometimes shale. The banding might have resulted from seasonal changes in organism activity.
Iron Ore Pellets
Pellets are small balls of iron ore used in the production of steel. They are made with technology that uses the powder that is generated during the ore extraction process, once considered wasteThe pellets are used in the production of steel which is used in the construction of bridges, cars, planes, bicycles, household appliances and much more. But, before this, the ore goes through a blast furnace that only works when air can circulate freely. For this reason, the material needs to be big enough so that there are spaces between each piece. On top of this, the ore needs to be strong enough not to be crushed thereby obstructing the blast furnace. Thus, the production of pellets is fundamental to the steel production process.
Pig Iron
Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. Raw iron is alloyed with a variety of elements (such as tungsten, manganese, nickel, vanadium, chromium) to strengthen and harden it, making useful steel for construction, automobiles, and other forms of transportation such as trucks, trains and train tracks.
Sponge Iron
Sometimes known as direct-reduced iron, sponge iron is a product that is produced using iron ore. The iron ore is often in the form of pellets or lumps, and is subjected to a reduction process that is created by the use of a reducing gas that emits from coal or a natural gassource. This type of iron can be produced in several different types of furnaces, including coke or charcoal ovens, blast furnaces, and basic oxygen furnaces. There are several benefits associated with sponge iron that allow it to compete effectively with other types of smelted irons. One has to do with the actual composition of the final product itself. For example, this type of iron is considered richer than pig iron, another type of iron commonly produced in blast furnaces. Direct-reduced iron has a slightly higher iron content, which often makes it better suited for use in electric furnaces.
The major rock types mined for the production of metallic iron are massive hematite, pisolitic goethite/limonite, which provide a 'high-grade' ore, and banded metasedimentary ironstone, magnetite-rich metasomatite, to a much lesser degree, rocks rich in siderite, rocks rich in chamosite which provide a 'low-grade' ore.
High-grade ore
Currently most of the iron ore mined in the world comes from large deposits of massive hematite rock formed by the in situ enrichment of a protore already enriched in iron, most commonly a banded iron formation (BIF). The consensus model for formation of massive hematite ore is enrichment by the passage of fluids, which remove the non-iron-bearing minerals (dominantly chert), to a much lesser extent add iron minerals. There are several variants of this model with the most accepted being enrichment by supergene processes. Recent models suggest enrichment by mass sideways and upward migration of dominantly superheated meteoric waters perhaps with a minor magmatic component. High-grade ore generally has a cut off grade of ~>60% Fe. Historically it has provided a direct feed to smelters either as a raw lump or fines, also in a processed form such as sinter or pellets. There are emerging markets for new varieties of feedstock. Examples include sintered iron carbide and 'DRI' ore, which is natural ore with Fe >69% and low levels of specific trace elements suitable as feed to 'direct reduction' smelters.
Low-grade ore
Low-grade ore is a term applied to iron-rich rocks with cut-off grades in the range of 25 to 30% Fe. It was the main supply of iron ore for many centuries of the World's early history of production of iron.The dominant economic iron mineral in low-grade ore is magnetite. The ore may be easily beneficiated by a process know as wet-magnetic separation BIF with hematite as the dominant iron mineral may also be beneficiated through wet hydrometallurgical processes though it rarely is due to economic constraints.
